1. Field of the Invention
The invention relates to a plug for a plug connection for optical waveguides. Such plug connections are required wherever continuous optical waveguides cannot be provided, that is to say, for example, in the case of couplings between railway cars, etc.
2. Discussion of the Prior Art
FIG. 1 shows examples of known plugs from the prior art such as those used in standard applications. FIG. 1a shows a plug connection in which two pins 1a and 1b are inserted together into a centring coupling sleeve 2a. This state should be achieved in principle in the case of all such plug connections, since the pins 1 are highly accurate guide parts, in the centre of which the thin optical waveguide is held. The polished ends of the particular optical waveguides must as far as possible be centred opposite one another in order to avoid transmission losses during light transmission. It is also important for the pins 1 or the ends of the optical waveguides to approach one another as closely as possible. The last-mentioned condition is well fulfilled by a construction according to FIG. 1c, where at least one pin 1c of a plug connection is spring-loaded in the connecting direction. When two plugs are united, similarly to the position in FIG. 1a, such a pressure spring 3a ensures that the pin 1c is pressed under spring force against the assigned second pin (e.g. 1a), so that the distance between the two pins 1 is minimal.
These known arrangements give rise to a technical problem:
If the plugs or pins 1b or 1c are pulled out of their plug connections, the pins 1 or the ends of the optical waveguides are exposed to the atmosphere since the sleeve 2a remains on the pin 1a in the case of FIG. 1a and since the pressure spring 3a according to FIG. 1c pushes the pin 1c forwards into the position shown. The optical waveguides or the ends thereof are without protection in these positions and can easily be contaminated or damaged by moisture, dust, dirt or body fluids--when the pin 1 is touched with the fingers--which may lead to transmission losses or failures on subsequent reuse of the plugs.
The only known protection against this is the mounting of a cap 4 on the pin 1 (FIG. 1b). However, it is precisely the mounting of this cap that is dangerous since, in the event of a slight lack of attention, the fitter may, for example, slip and, instead of the cap 4, his fingers will touch the end of the pin. Apart from this, the pin 1 is unprotected until the cap 4 has been mounted.